An outboard engine generally comprises a bracket assembly that connects the drive unit of the marine outboard engine to the transom of a boat. The drive unit includes the internal combustion engine and propeller. The outboard engine is typically designed so that the steering angle and the tilt/trim angles of the drive unit relative to the boat can be adjusted and modified as desired. The bracket assembly typically includes a swivel bracket carrying the drive unit for pivotal movement about a steering axis and a stern bracket supporting the swivel bracket and the drive unit for pivotal movement about a tilt axis extending generally horizontally. The stern bracket is connected to the transom of the boat.
To steer the drive unit, some watercraft propelled by one or more outboard engines use a mechanical steering in which push-pull cables are operatively connected between the steering wheel and the drive unit. In other watercraft, hydraulic lines run from the steering wheel and connect to a hydraulic actuator on the bracket assembly or the transom of the watercraft that is used to steer the drive unit. In both cases, a rotation of the steering wheel is directly translated into a corresponding rotation of the drive unit about the steering axis.
Other watercraft propelled by one or more outboard engines use what is commonly referred to as a steering-by-wire system. In such an embodiment, a steering wheel position sensor senses a position (or a change in position) of the steering wheel and a signal representative of this position is sent to a steering actuator on the bracket assembly or the transom of watercraft. The steering actuator then steers the drive unit based on this signal. In some embodiments, the steering actuator is an electrical actuator. In other embodiments, the steering actuator is a hydraulic actuator and an electrically powered hydraulic pump. In some embodiments, the hydraulic actuator and pump are provided in addition to a system having hydraulic lines running from the steering wheel to a hydraulic actuator to form what is sometimes referred to as a hydraulic power steering system.
In such steering-by-wire systems, the rotation of the steering wheel and the steering of the drive unit are decoupled. It is therefore desirable to obtain some kind of feedback in order to know that the drive unit has actually been steered to a position corresponding to the position of the steering wheel.
Some outboard engines using steering-by-wire systems are therefore provided with steering position sensor sensing an angular position of the drive unit about the steering axis. Most outboard engines are steered by linear actuators (hydraulic or otherwise). In such outboard engine, the steering sensor senses a linear position of a movable part of the linear actuator. The linear position of the movable part of the linear actuator is then converted to a corresponding angular position of the drive unit. However, some outboard engines are now provided with rotary hydraulic actuator, such as described in U.S. Pat. No. 7,736,206 B1, issued Jun. 15, 2010, the entirety of which is incorporated herein by reference.
There is therefore a need for a steering position sensing system adapted for outboard engines using a rotary hydraulic actuator to steer the drive unit.
It would also be desirable to have a steering position sensing system sensing an angular position of the drive unit directly, thus avoiding the conversion from linear position to angular position that is necessary with the above described linear position sensor.
Also, linear steering position sensors typically have a movable part and a fixed part. The movable part slides in and out of the fixed part. The interface between these two parts can lead to water entering the fixed part, which usually contains sensitive electronics. Furthermore, water inside the fixed part can hinder the motion of the movable part. It is possible to provide seals, but these add to cost and complexity of the sensor. Also, water may get past the seals over time as they wear out, thus requiring replacement of the seals or of the entire sensor should the electronics become damaged by the water.
Therefore there is a need for steering position sensing system that addresses the issue of water intrusion in the sensor.